1. Field of the Invention
The present invention relates to a process for the preparation of motilin-like polypeptide, a recombinant DNA therefor, and a plasmid, in which the recombinant DNA is inserted.
The polypeptide can be used as a pharmaceutical agent and more particulaly, for curing gastroenteropathies.
2. Related Arts
Motilin is one of peptide hormones, first isolated from mucous membrane of porcine upper small intestine, and its amino acid sequence determined by Brown J. C. et al ["Gastroenterology" Vol. 62, pages 401-404 (1972) and "Can. J. Biochem." Vol. 52, pages 7-10 (1974)]. The porcine motilin consists of 22 amino acids and has a molecular weight of about 2700.
The present inventors have succeeded in isolating cloned cDNA which encodes human motilin precursor, the nucleotide sequence including therein a part designating the amino acid sequence same with that for the porcine motilin, so that it has been made apparent that the human motilin has the same amino acid sequence same as the porcine motilin [Jap. Pat. No. Sho 63-276489(A) which corresponds to U.S. Pat. No. 4,985,356 and European Pat. Appln. No. 88107108.8].
As physiological actions of the motilin, a hypermotility action of digestive tract and contracting action of gastroduodinal and colonic smooth muscle therein have been well known. As the hypermotility action, it has been reported that the rate of gastric emptying is shortened ["Gastroenterology" Vol. 80, pages 456-460 (1981)] and as the contracting action of smooth muscle in the digestive tract, it has been known that the motilin shows a strong contracting action to rabbit and human gastrointesinal tract, independent from a neurosystem. Moreover, no report has been issued on any specific side-effect. Therefore, it has been considered that the motilin is useful for curing gastroenteropathies during the period of post-operation and for diagnosis thereof. In connection with this, please note that prostaglandin has widely been employed for curing gastroenteropathies, which drug may show a relatively strong side-effect.
It has been also reported that chemically synthesized motilin analogues--the methionine in position of 13 being substituted with either leucine or norleucine--show biological activities similar to pure native porcine motilin ["Scand. J. Gastroenterology" Vol. 11, pages 119-203 (1976) and others] and thus it has been considered that the methionine at 13-position has almost no influence on activity of the motilin.
Motilin according to widely accepted technical art has been obtained through extraction from porcine organ tissue and thus it was quite difficult to obtain motilin in a large amount by such methods. Since motilin is polypeptide consisting of 22 amino acids, a large scale production is difficult, even if chemical synthesis shall be applied. Namely, the motilin has not actually been employed for clinical use, due to its poor productivity, despite an effectiveness as an agent for curing gastroenteropathies has been expected.
Therefore, various studies have been made for preparing polypeptides having motilin-like biological activity, with a reasonable cost, by utilizing the so-called "Bio-technology" [Jap. Pat. Nos. 63-71195(A) and 1-102096(A)].